New Millennial Warm Pool Foraminifera Study

Hot off the press this week is a study on foraminera over the last millennium in the Indo-Pacific Warm Pool – something that you’d think would be relevant to Hansen’s attempts to splice modern instrumental records to core tops ending in the Holocene Optimum. Newton et al 2006 have the following abstract:

Planktonic foraminiferal Mg/Ca and d18O derived sea surface temperature and salinity records from the Makassar Strait, Indonesia, show a long-term cooling and freshening trend, as well as considerable centennial-scale variability during the last millennium. The warmest temperatures and highest salinities occurred during the Medieval Warm Period (MWP), while the coolest temperatures and lowest salinities occurred during the Little Ice Age (LIA). These changes in the western Pacific, along with observations from other high resolution records indicate a regionally coherent southern displacement of the Inter-tropical Convergence Zone during the LIA, with more arid conditions in the northern tropics and wetter conditions in the southern tropics.

They report:

The core used for this study, MD9821-60, was collected aboard the Marion Dufrense in 1998 as part of the IMAGES coring program. It was collected at 5 12.07 S, 117 29.20 E from a water depth of 1185 m. This depth is well above the present-day lysocline [Farrell and Prell, 1989], which allows for excellent carbonate preservation. Although the uppermost sediments representing roughly the last 150 years were lost during the coring process, the average Holocene sedimentation rate at this location is well over 100 cm per 1,000 years, making it an ideal core for high resolution studies of hydrographic changes in the Makassar Strait….

The core was sampled continuously at 1 cm intervals, providing a time resolution of less than 10 years

I would have thought that the loss of the sediments for the last 150 years would make it less than ideal for high-resolution studies. It would certainly be nice to see some results for the last 150 years. I’m curious as to how they know that 150 years were lost. In mineral exploration, the core logs are essential parts of the process and lost core is marked on the original core log. There is information on hole MD9821-60 at the IMAGES site, which provides considerable information on the core, but does not say that the top portion of the core was lost (although the length of recovered core is less than the length of the core.)

Their dating model notes an ash layer at 15 cm which is ascribed to the 1815 Tambora eruption. They don’t say why it is dated to the 1815 Tambora eruption as opposed to the 1884 Krakatoa eruption. This might make a difference to the dating. I’d like to ensure that they have not merely assumed that 150 years is missing because of an expectation that modern proxy values would exceed MWP values (which they obviously don’t here.)

Here’s their Figure 1 showing dO18 and Mg/Ca results. They report:

Mean temperature decreased by approximately 1 deg C during the last 1,000 years, while salinity decreased by 0.9. This is consistent with an overall trend of decreasing salinity and temperature in the IPWP throughout the Holocene [Stott et al., 2004].

Taking these results at face value, they evidence a remarkable warming of the Warm Pool by almost 2 deg C in less than a decade at the turn of the 19th Century. It would be interesting to see if there are contemporary historical evidence of this remarkable event.

They attribute changes in the Warm Pool to changes in the north-southing of the ITCZ – something which I proposed as an explanation for Kim Cobb’s coral values as an alternative to a cold MWP Pacific – which is obviously nowhere in evidence here.

33 Comments

As far as knowing which erution the 15cm ash belongs too, there are a couple of ways to know. If the ash sample is sent to the right person (Sarna at UW), he can tell you not only which volcano an ash came from , but which eruption it came from. He is the Guru of ash dating and may have some ex-students who are carrying on his techniques. Does the paper say how the dated the ash? If it was only via C-14 dating , without an ash expert looking at the ash under the microscope, that would seem a bit fishy? Seems they would have the budget to send a sample to Sarna or one of his type.

Lost. Lost? Lost! Fascinasting the way you zero in on these attempts to slide things under the rug Steve. Sounds like another email is called for. I have been wondering if Lea had formulated a better response on why he used a calibration equation on Forams that was 10 years out of date and overestimated absolute temperatures by 0.3C, apart from ‘to be consistent with the last time’?

Its my understanding that core top “losses” are fairly common with piston coring because the piston disturbs the less compacted upper layers of sediment. The mud may be there but so mixed as to not be useful. How they know its a 150cm loss is another question. Perhaps by comparison with another nearby core that was much less disturbed?

Another useful item to know is the depth of bioturbation in the sediments. If the biota turn over the mud to a depth of several cm then the signal (microfossils, chemistry, etc.) is going include information deposited at different times producing a smoothing effect. High sed rates could minimize this, but maybe not in relatively shallow water. Its an issue that seems to be addressed very rarely; however, it could be of importance in high-resolution situations.

Dating also can be done by comparing/matching microfossil frequencies and chemical signals (dO18 and carbonate percent) at various depths to nearby cores that have been dated. Its a good way to cross-check ash layers and C14 dates.

Having done a few cores myself I can understand that the top layers would be more perturbed. But why not analyse and report the results none-the-less? I can understand not reporting them in a monitoring context, where you are sampling routinely, but not in this context. At least say what you mean by lost.

The paper in question is Magnitude and timing of temperature change in the Indo-Pacific warm pool during deglaciation, Katherine Visser, Robert Thunell & Lowell Stott. It is published as a “Letters to Nature” in Nature Magazine, and is available by subscription.

My question is, why do these guys always try to oversell their papers? Overall, at first glance this seems like a reasonable paper. But then they say:

What are the broader implications of our findings concerning the
magnitude and timing of SST change in the Indo-Pacific warm pool
during the last two glacial–interglacial transitions? The global
atmosphere is very sensitive to changes in tropical SST (2), particularly
with regards to its effect on fluxes of heat and water vapour to higher
latitudes. The tropics, in general, and the Indo-Pacific warm pool, in
particular, are the main regions from which water vapour is
supplied to the atmosphere. As water vapour is one of the main
greenhouse gases, substantial variations in the moisture content of
the atmosphere associated with past changes in SST can be expected
to have had a major role in global climate change.

As you can see, other than a strong correlation with the air temperature directly above it, the Warm Pool has no strong positive correlation with SAT anywhere else. It is correlated with cold SAT in several regions … but this will not affect the overall climate, as these will average out with the warm air over the

And they have used a very shaky reference (2) to back up their ideas, namely, Pierrehumbert, R. Climate change and the tropical Pacific: The sleeping dragon wakes. Proc. Natl Acad. Sci. 97, 1355–1358 (2000), available here. This contains any number of curious claims, including the following:

The warm pool has no intrinsic cloud, evaporative, or thermodynamically based “thermostat,” and in the absence of heat exports to the extratropics would escalate from its present temperature of 29°C to temperatures of 47°C or even more (7, 8).

Huh? Even if this might be true, there’s no way that the tropics will stop exporting heat to the extratropics. It’s like saying “If the earth stopped radiating, it would heat until the trees caught fire.” True … but meaningless. He also says:

One of the more exotic possibilities is that a strengthening of the temperature contrast between the warm
pool and the cold tongue could lead to a complete breakdown of the system of tropical easterly trade winds
known since time immemorial. This breakdown could happen, if a tropical sea surface temperature anomaly
forces a Rossby wave that carries easterly pseudomomentum away from the tropics, leading to a local
westerly acceleration. If the forcing were strong enough, the westerly acceleration could overwhelm the
easterly Coriolis acceleration caused by equatorward drift in the Hadley cell, whereupon the normal tropical
winds would be replaced by a westerly superrotation. If the westerlies were to penetrate to the surface, the
normal equatorial upwelling in the ocean would be replaced by downwelling, and other far-reaching climate
changes would ensue. The superrotating state is well documented in idealized two-layer models (24) and has
been found by several investigators employing realistic multilevel general circulation models (I. Held and
D. Hartmann, personal communications; see also ref. 25). There is no evidence that a westerly superrotating
state has ever occurred in any climate of the Earth’s past, but then again, in some regard the particularly high
CO2 climate with glaciated poles that we are now approaching is different from any that has ever before
held sway on the planet. If one is tugging on the dragon’s tail with
one must be prepared for the unexpected.

This is not science, this is science fiction. He is warning us against a climate state that has never occurred except in climate models. And this is the paper that Visser et al. are citing to back up their claims? …

This core was almost certainly collected with a Calypso corer deployed from the Marion Dufresne. This corer can collect fantastically long cores with a single drive, unfortunately it typically overpenetrates, losing the surface-water interface. The estimated of 150 cm lost is probably from an extrapolation of the sedimentation rate. Other corers (box corers) are often deployed specifically to get the uppermost sediment, I don’t know why this was wasn’t done here – perhaps the box cores were too short to overlap with the long core.

Well, the paper I reviewed above was not the paper Steve M. was discussing … ah, well, it was an interesting paper nonetheless.

Finally tracked down the right paper. One thing I noted was that Hansen had said that the G ruber Mg/Ca standard error was 0.6°C … but these folks agree with Dekens that the standard error is 1.2°C, which gives a 95% confidence interval of 2.4°C.

Here’s the Newton et al. results, compared with the modern sea surface temperatures at the site where the core was drilled. Note that the time scale is reversed from that above.

The error bars show the 95% confidence intervals …

One peculiarity of the chart Steve M. shows above in Figure 1A. The relationship between SST and Mg/Ca ratios is logarithmic, but the scales for the two are linear … so at least one of them is wrong. My money’s on the Mg/Ca scale being incorrect.

re #11:
Both axes are correct.
The relationship between Mg/Ca and temperature is logarithmic, but over the 3.5C range in figure 1A, it is effectively linear. The equation from Dekens et al 2002 is Mg/Ca=0.38*exp(0.09*SST- 0.61*(core depth km)-1.6°C)

I’m a bit confused about the equation you give. is the exp(…) part supposed to be 10^(…) or e^(…) or .38^(…) or what? In any case whatever’s in the parens should be dimensionless and it shows two parts in deg C and one in km. Does that just mean the three factors .09, .61, & 1.6 have the appropriate /deg C or /deg km attached? If so I’d think it’d be less confusing to simply drop the deg C from the last one).

RE: #8 – See my “snake oil salesmen” comment on the TOPEX thread. I am growing increasingly disgusted with the emerging picture of widespread chicanery in the real of so called “climate science.” Think long and hard regarding my continued use of “so called” and the enclosure of this reputed science in with quotation marks. I’m loaded for bear.

re #12
exp(X) is the same as e^X
In the Pacific, there is more dissolution of calcite in deeper water. During dissolution of calcite, Mg is lost faster that Ca, altering the Mg/Ca ratio. The depth term in the Mg/Ca SST calibration equation (from Dekens et al 2002) corrects for this dissolution.
I lost a bracket last time – the equation should be Mg/Ca=0.38*exp(0.09*[SST- 0.61*(core depth km)-1.6°C])
The units are not given in the paper, but I guess they are:
0.61 °C/km
0.09 °C-1
0.38 unitless

with regards to the CA discussion on “New Millennial Warm Pool Foraminifera Study”, my recent publication with Rosanne D’Arrigo may add to the discussion about what climate may have been doing over the last 150 years or so in the Warm Pool region.
We show a much slower temperature increase (0.2 degrees C / 100 years) for the last century, but show clear volcanic signatures in the data.

To be honest though, out study was developed from only a few proxy series, so I am sure the story could change somewhat as more data are added in the future.

#4. Then presumably there is some core that resolves the last 150 years in the Warm Pool. Do you have a reference?

Sorry, don’t have any references on this. I used to process core samples for the CLIMAP and SPECMAP projects long ago, but since have moved on to other things and have only an amateur interest now. Many cores were taken world-wide by various vessels during the 50s, 60s and 70s. There likely are others relatively nearby that may or may not have been sampled. I haven’t had the time to read it yet, but this study seems to report data from just the one core. References to “lost” sediment and brevity of description would be understood by other paleoclimatologist who read between the lines, but its easy to see how others not in the paleo community would view it as slipshod work. Rather than being a definitive study, this paper may just be a quick write-up of interesting results.

I didn’t mean to suggest that the core loss was necessarily slipshod pactice. HOwever to characterize a core with the last 150 years missing as an “ideal” core for millennial commentary does seem implausible. Why wouldn’t they report on a core with no missing core at the top?

Steve,
I am thick skinned enough to survive any comments (positive or negative) made by TCO. My earlier e-mail to you (which you posted on CA) was made purely in an attempt to address the issue of ‘missing’ information over the last 150 years in the Newton et al. paper. Our study, I think, does this quite nicely.

TCO,
I do not think Steve is “kissing my ass” – so quaintly put I might add. Steve and I certainly do not agree on all things, but we try to keep our discussions at a polite professional level. Something that you should perhaps keep in mind once in a while.

Willis,
re your chart in 11 shows the range of the blue line measurements (31deg – 28deg) is less than the magnitude of the measurement error(+-2.5). Does that mean that the actual paleo temps have an equal probability of having:
1)a warming trend of about 5 degrees,
2)a similar cooling trend,
3)a fluctuation within 5 degrees, or
4)no change at all?
All I see in the graph of the paleo record is SST was about 27 to 32 degrees. Or is there some information in the data that I am not understanding?

Rob, my comment rather then polite and professional was provocative and casual. Key thing, though is why are you reporting on foramina? You don’t even have tree rings down. When I see people chasing fads like that (in and out of High Tc superconductors for instance…from someone not even an oxide chemist), it makes hair on the back of my neck go up. Makes me wonder how good a job they will do. Although addressed to you, the issue is more general.

Oh…and if this is just jotting down an interesting result, why is it in Nature? I know…Nature lubs dat climatology. And individuals love getting Nature pub cred…rather than actually loving solving problems.

I sorta wonder what Rob’s comments on “volcanic signature” are supposed to mean. It sure sounds like he doesn’t like the low temp rise and wants to blame volcanos. I wonder if he had the same exact ash content, but the floramins had played along better, if he would say there was “volcanic signature”.

I am not sure what TCO is talking about now. I was not reporting on foraminifera.
My study with Rosanne D’Arrigo is a multi-proxy study utilising tree-rings and corals to reconstruct SSTs in the Warm Pool region. It is not in Nature (nor is the Newton study for that matter).
I only mentioned the volcanic signatures as we see evidence for multiple volcanic events in the 19th century.
You have obviously not read the paper TCO.

#29. D’Arrigo and Jacoby have been working the PAcific for years, including Indonesia. ONe may have other criticisms, but not these particular ones. TCO, please look at their paper before mouthing off about it. That’s why I deleted your original comment – aside from being rude, it was ignorant in the literal sense of the word. I was hoping to save this pointless exchange.

On a substantive point, I really doubt that Rob’s study can “fill in the 150 year gap well”. All of these proxies have different behaviors and splices are very much not to be trusted in this business. You want to see the record all the way up through instrumental time, so that you can even tell if the proxy is a proxy. That’s why the recent sediment is needed, Rob.

I didn’t mean to suggest that the core loss was necessarily slipshod pactice. HOwever to characterize a core with the last 150 years missing as an “ideal” core for millennial commentary does seem implausible. Why wouldn’t they report on a core with no missing core at the top?

Its the fast sedimentation rate that makes it useful for high resolution studies. Typically 1 cm slices are processed, so in this core there would be fewer years represented in a slice than for a mid-ocean core with sed rates closer to 1 cm per 1000 years. The wording of the sentence implies the lost years are only a minor flaw in an otherwise “good” core. I surmise that this was the best one they had and, at least in their judgement, suitable for drawing their conclusions. 850 out of a thousand years isn’t too bad, even if not perfect.

You know, looking at Rob’s paper’s preamble and some of Cobb’s work…I get this suspicious on El Nino research. I start to wonder that people are essentially producing proxy climate studies, that have direct relevance to the AGW debate (via assessing variability), but that they don’t want to openly say this and let things sink or swim on there own. So the call them El Nino research.

On a more light note, I was going to accuse Rob of chasing after Polyenisian hotties…now I think he likes Kim.

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[…] SST proxy ending in 4320 BP based on a partially dissolved core.’ A couple of months ago, I mentioned a new paper by Newton et al (including L Stott) with a high Warm Pool MWP and briefly discussed […]